Removing airborne pathogens and environmental allergens is very important in environments that require high levels of air purity, such as in hospitals and in houses of people suffering from severe allergic responses to the aforesaid allergens. Typically, devices in the form of masks or in-air duct filters filter out particulate material during either air circulation or, in the case of facemasks, during inhalation and exhalation. The facemasks and air duct filters temporarily capture the pathogens and allergens, and particulate matter such as dust, on a surface of a filtering material. Once the filters reach a threshold limit or after a single use, they are typically discarded or in some cases, cleaned and reused. Many designs of filtering devices exist, examples of which are as follows:                U.S. Pat. No. 1,319,763, issued Oct. 28, 1919, to Drew for “Air filter for wall registers”;        U.S. Pat. No. 3,710,948, issued Jan. 16, 1973, to Sexton for “Self-sustaining pocket type filter”;        U.S. Pat. No. 3,779,244, issued Dec. 18, 1973, to Weeks for “Disposable face respirator”;        U.S. Pat. No. 3,802,429, issued Apr. 9, 1974, to Bird for “Surgical face mask”;        U.S. Pat. No. 4,197,100, issued Apr. 8, 1980, to Hausheer for “Filtering member for filters”;        U.S. Pat. No. 4,798,676, issued Jan. 17, 1989, to Matkovich for “Low pressure drop bacterial filter and method”;        U.S. Pat. No. 5,525,136, issued Jun. 11, 1996, to Rosen for “Gasketed multi-media air cleaner”;        U.S. Pat. No. 5,747,053 issued May 5, 1998, to Nashimoto for “Antiviral filter air cleaner impregnated with tea extract”;        U.S. Pat. No. 5,906,677, issued May 25, 1999, to Dudley for “Electrostatic supercharger screen”;        U.S. Pat. No. 6,036,738 issued Mar. 14, 2000, to Shanbrom for “Disinfecting gas filters”;        U.S. Pat. No. 6,514,306 issued Feb. 4, 2003, to Rohrbach et al. for “Anti-microbial fibrous media”.        
The aforesaid designs suffer from a number of important drawbacks. Disadvantageously, in the above-mentioned designs removal of the dirty filter or the facemask after use may cause non-immobilized pathogens or particulates to be dispersed into the air immediately around the user, which, if inhaled may be hazardous to the user. In addition, the designs may not immobilize the air borne pathogens and kill them in situ. Some of the designs incorporate viscous material into the filter material to capture particulate material. Some designs incorporate complex arrangements of filters inside cartridges, which may be impractical for use in air ducts or in facemasks. In some cases, fiberglass is used as part of the filter medium, which may be harmful to humans if located near the nose and mouth. In one design, disinfectant soaked cotton wool appears to be located in an air duct for aerosolizing into a room to maintain moisture content. Use of such a wet disinfectant may be harmful to humans in close proximity to the disinfectant and may not be appropriate for use in a facemask. Another filter media uses fibers having cavities filled with antibacterial agent for slow release there from. Another design discloses the fiber manufactured with antibacterial agent therein that freely detaches there from upon blooming of the fibers. These fiber designs have the problem of a rapid lost of their antibacterial activity upon cleaning or washing thereof.
Accordingly, there is a need for an improved microbicidal air filter.